General & Technical Information


Inigo Jones uses mainly blue-grey welsh slate for the majority of its products. Welsh slate is a natural material around 500 million years old. It is chemically inert, non-porous and damp proof, has great intrinsic strength and cannot warp, shrink or rot. Slate is found mainly in the mountainous area of North Wales and Cumbria. Its most distinguishing characteristic is its natural cleavage, which permits very fine limits to be achieved in its shaping and fabrication. This makes it an ideal material for monumental, architectural and craft items. Inigo Jones is a guarantee of the best in slate for whatever purpose.


Inigo Jones ensures that the selected slate will fit the intended purpose. Over the years, Inigo Jones have taken pride in the quality of welsh slate and the regard and esteem in which it is held by those who use it. However, opinions and usage are not always enough and occasionally proof of quality is required. To this end we have provided some useful technical information.

Thickness to Weight ratio

Thickness m2/tonne ( approx ) Kg/m2
12mm 28 36
20mm 19 55
25mm 14 72
38mm 9 113
50mm 7 146
75mm 5 220

Maximum Slab Dimensions

The largest size available depends greatly upon dimensions of block that can be extracted at one time. However, as a general rule, the maximum size we have is as follows :-

12mm 1200 x 600mm
20mm & over 1600 x 800mm

Larger sizes are sometimes available on request.


All slates used by Inigo Jones conform to BS 5642 and BS 680.


When slate is used externally we do not recommend sealing but the slate should be regularly washed with clean water. For internal hearths window boards and craft items we recommend slate seal that we sell in a 100ml plastic bottle. For internal flooring we recommend Selexel AO11 which we sell in a 500 ml plastic bottle


Welsh Slate is a natural material which is hard and durable and chemically inert. The slate is usually supplied by Inigo Jones as a finished product which requires no further machining.

Handling and Working Precautions
Slate products are generally of such size that an individual item may be of some weight. Protective gloves should be worn when handling and any sharp edges treated with care. Protective footwear should also be worn.

Machining & Drilling
These processes create a fine spoil of dust if carried out dry and as this dust contains quartz, the inhalation should be avoided. If it is not possible to carry out the cutting as a wet process, then dusk masks, to BS 2091 Type B, should be worn. Ideally such work should be carried out in a well ventilated area.

Injury or Cuts
In the event of injury or cuts, the normal First Aid precautions will suffice.

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